The present invention relates generally to semiconductor integrated circuit designs and dies, and more particularly to extendable semiconductor integrated circuit designs and dies.
Custom design of chips for integrated circuitry allows a chip designer the opportunity to optimize circuitry within a chip to account for speed, footprint and power, and yield issues. Thus, custom design of chips for integrated circuitry generally provides chips operating at the highest clock rates, having the lowest footprint and power consumption, and potentially the highest manufacturing yields. Such customized chips provide the opportunity for increased chip functionality and decreased manufacturing costs, particularly for high volumes of chips.
Definition, design, and test of custom chips can be a long, laborious, risky, and expensive process. Custom design flows generally include RTL coding, synthesis, timing analysis, place and route, as well as verification within and at potentially each step. Errors and problems may occur at each of these steps, and each of the steps and other steps or indeed the entire process, may need to be revisited, possibly multiple times. Moreover, depending on any particular design, yield may be adversely effected by design flaws or other inadequacies in the design.
The use of IP blocks, such as third party IP blocks, within a custom chip can reduce risk and design costs. The use of third party IP blocks can also be problematic, however. The third party IP block may have been designed using a different design flow than that used for the rest of the custom chip, introducing the possibility of errors and increased integration effort in integrating the third party IP. For example, third party IP may have been modeled using different process parameters than those used for the rest of the chip, potentially making the models, and thus expected chip operation, inaccurate. The third party IP block may also not be optimized for the manufacturing process used for the chip, introducing potential yield issues.
An alternative to a custom design process is the use of, for example, a field programmable gate array (FPGA). FPGAs, however, generally exhibit reduced clock speeds, resulting in reduced performance, and increased footprint, which often implies increased power consumption. In addition FPGAs often require increased production costs, considering that the FPGA chip generally includes gates for a wide variety of uses. In addition, FPGAs may have limitations in terms of floor space available for on-board memory or other specific items, further restricting the scope of use of FPGAs.
The possibility of including at least some metal programmable elements, such as phase-locked loops (PLLs), on an integrated circuit die is known. During fabrication a PLL with particular characteristics, selected of a few possible characteristics, may be devised by interconnecting particular components available to make up the PLL. In many instances, however, merely changing an aspect of an operation of a particular component on a die of an integrated circuit is insufficient to provide for increased capabilities for a range of possible functions.